1. Field of the Invention
This invention relates generally to systems and devices for sensing high accelerations or impact events. The invention is particularly drawn to providing systems and devices incorporating certain compounds, known to produce light radiation when subjected to mechanical energy and to systems and devices wherein these compounds are dispersed throughout a frangible porous material.
2. Statement of the Problem
Under certain circumstances, it is desirable to provide a mechanical or electrical system with embedded sensor/indicators which are, and remain, electrically isolated, and do not rely on sources of electrical power for activation. This is because there is a desire to prevent compromise to the safety or integrity of the system through an external power supply connector, to prevent unauthorized access, or to avoid the need for entry into the system in order to periodically replace limited life reserve sources of electrical energy.
An indicating sensor providing a pulse of detectable light would be a useful method for verifying whether or not various internal system functions have activated, or whether or not certain parameters of in the internal system environments had been exceeded. Events such as movement of mechanical actuators, pistons, or gears, the activation of an explosive actuator, acceleration loads such as impact events (beyond a predetermined level), and the like, are examples of binary threshold events to which a shock-sensitive indicator device could be applied.
It is known that all bodies radiate electromagnetic energy, so-called black body radiation or thermal emission, i.e., xe2x80x9cheat.xe2x80x9d That is, hot bodies that are self-luminous solely because of their high temperature represent a special case and are said to emit visible light by incandescent radiation. All other forms of light emission are said to be luminescent and are dependent upon the specific material. The luminescence process itself involves 1.) absorption of energy; 2.) excitation; and 3.) emission of energy, usually in the form of radiation in the visible part of the spectrum. Therefore, some source of energy is required in order to trigger and/or to continue light emission since such emissions represent a net loss of energy by the body. Most of these kinds of luminescence are classified according to the source from which this energy is derived, e.g., the light from a gas discharge lamp, produced by the passage of an electric current through the ionized gas is said to be electroluminescent.
In particular, light which results from energy supplied to a material in the form of mechanical energy, is known as triboluminescence; also referred to as mechano-luminescence or fracto-luminescence. The effect is thought to arise through fracture or cleavage of individual crystals of a certain class of solid materials together with a concomitant electrical breakdown. However, the effect is poorly understood and may be the result of any input of mechanical energy which provides frictional force, or some amount of strain energy, to a particle of the identified class of materials, even of non-crystalline materials. Furthermore, the effect may arise also as the result of an electric charge separation as new interfacial surface is created as the material is either cleaved or breaks free and separates from a surrounding host matrix in which the material is embedded. In either case, it is known that when mechanical energy is imparted to certain compounds these compounds emit light energy and that this effect is intense enough in certain materials to be easily detectable. The observed range of light wavelengths runs from red to deep ultraviolet.
3. The Prior Art
While triboluminescence is a well known phenomenon, its application to physical sensors is limited. U.S. Pat. No. 4,020,765 to Glass, et al., describes a munitions fuse relying upon a light signal generated by ordnance of a triboluminescent material coating the inside of the ordnance nosecone as the ordnance strikes a target. U.S. Pat. No. 5,905,260 to Sage, et al., describes a sensor for detecting damage in aircraft structures by connecting a piece of light guiding optical fiber with a triboluminescent material. Damage to the structure is recorded by light pulses generated by fracture of a plurality of triboluminescent crystals. Neither of these patents, however, describe a sensor-indicator comprising a comminuted, triboluminescent powder dispersed within a frangible media material.
Triboluminescent light may be useful where there is a need to record the response to a mechanical event without the need for relying upon a source of electrical power.
A principal object of the present invention is to provide systems and devices incorporating triboluminescent constituents for providing a transient source of light emission.
Another object of this invention is to provide a systems and a device for generating a source of light emission which is subsequently converted into an electrical signal.
A further object of this invention is to provide means for containing one or more triboluminescent constituent materials and means for suspending said materials in a low density, frangible solid media.
This invention comprises a device for providing a light indicator display comprising a triboluminescent compound. The device comprises a frangible foam substrate within which the triboluminescent compound has been dispersed. The device is further adapted to crush the frangible foam substrate upon the occurrence of a specific event.
These and other objects and advantages of the invention will become apparent and will be more fully set forth as the description thereof proceeds in the following specification and claims considered in connection with the attached drawings to which they relate.